Study on acid generation from polymer

Abstract

In the fabrication beyond the 32nm node, the uniform distribution of acid generators in a resist matrix is a serious concern. The incorporation of acid generators to polymers via covalent bonds has attracted much attention in order to overcome the compatibility problem of acid generators with polymers. We reported the reaction mechanism of acid generation in typical chemically amplified resists for ionizing radiation, such as electron beam and extreme ultraviolet. The simplest way to induce the same reactions in a single-component resist is the halogenation of polymers. We carried out a case study on the acid generation from polymers using brominated poly(4-hyroxystyrene) (Br-PHS). Br-PHS without an acid generator produced hydrogen bromide with the same amount as acid yield of PHS with 1.2mol% (4.1wt%) triphenylsulfonium-triflate. It was confirmed that Br-PHS with hexamethoxy methyl melamine worked as a chemically amplified resist without any acid generators. From the comparison among the acid yields of Br-PHS, PHS, poly(4-bromostyrene) and polystyrene, we concluded that the efficient acid generation from polymers requires a high reactivity with electrons, a high dissociation efficiency of counter anions, and an effective proton source, such as hydroxyl group.